This invention relates to dosing apparatus, arranged to permit the dispensing of a measured dose (volume) of a liquid from a container to which the apparatus is connected. Though the apparatus may be used with a wide variety of liquids, it finds a particular application in the dispensing of a pharmaceutical composition.
There is a need for a dispenser able repeatedly to dispense a pre-determined volume of liquid such as a pharmaceutical composition from a container usually in the form of a bottle, in which the liquid is stored. Though there have been several proposals for such dispensers, these all have various disadvantages and there is no satisfactory device available commercially which adequately fulfils all requirements.
According to the present invention, there is provided dispensing apparatus for dispensing a measured dose of liquid from an attached container, which apparatus comprises: an elongate casing defining a dispensing cylinder, one end of the casing being adapted for mounting on a container and the cylinder being open at the other end thereof, the cylinder being arranged to communicate with an attached container and having a liquid outlet port adjacent said one end; a plurality of dose indications provided on the external surface of the casing; a channel formed in the wall of the casing and extending along the length of the cylinder; a plunger having a piston co-operatively slidable within the cylinder for pumping liquid out of the attached container and through said outlet port; a dose control member connected to the plunger and arranged to slide in said channel; a dose-setting collar slideable over the external surface of the casing for alignment with a selected dose indication, the collar and dose control member being interengageable to limit the movement of the plunger away from said one end; and restraining means arranged between the dose-setting collar and the casing to secure the collar with respect to the casing at a selected dose setting.
It will be appreciated that, in use, the dose-setting collar is moved along the casing to a position corresponding to a required dose and is then secured at that position. Thereafter, on cycling the plunger from an initial position until its movement is blocked by the collar and then returning the plunger to its initial position, the required volume of liquid is drawn into the dispensing cylinder and then ejected therefrom.
In a particularly preferred embodiment of dispenser of this invention, the casing provides a cylindrical chamber and the dispensing cylinder is defined by a cylindrical tube mounted within the chamber at the one end of the casing, so that there is an annular clearance between the internal wall of the casing and the external wall of the tube. The channel may then be formed wholly through the wall of the casing, so as to communicate with the annular clearance. The dose control member may be a sleeve slideably mounted within the annular clearance and coupled to the plunger at the upper end thereofxe2x80x94that is, at the end of the plunger remote from said one end of the casing. Such as sleeve may have a first abutment which locates in the channel for sliding movement therealong as the plunger is cycled.
Preferably, the dose-setting collar defines a second abutment which runs in the channel as the collar is moved to the required dose setting and which is engaged by the first abutment on sliding the plunger away from the one end of the casing.
The restraining means advantageously comprises a plurality of stop elements arranged along the length of the casing, the collar being engageable with a selected stop element to be restrained against movement away therefrom. To increase the number of axial positions at which the collar may be secured with respect to the casing, such stop elements preferably are arranged helically around the casing. In a preferred embodiment, each such stop element is in the form of a recess or opening through the wall of the casing, the collar having a peg which is engageable in a selected recess. Such a peg may be mounted on an arm connected to the collar and moveable between free and secured positions. Alternatively, the peg may be formed on a band which encircles with clearance the casing, the band being resiliently deformable to move the peg away from the casing and so free the collar for movement along the length of the casing.
Advantageously the dispensing apparatus is provided with a mechanism which is difficult for a child to operate, so as to confer a degree of child-resistance to the apparatus. In one embodiment, the channel has an extension into which a part of the dose control member may be received, the release of the dose control member from the extension requiring a complex action. An alternative form provides a catch mechanism adjacent the upper end of the plunger and which is engageable with an abutment on the casing. In one embodiment, the release of the catch mechanism requires a transverse force to be applied to a catch member. In another, a press-button is provided on a cap for the plunger, which button when depressed releases the cap to permit the plunger to be drawn upwardly and charge the dispenser with a dose. In yet another embodiment, a cap for the plunger is held to the casing by interengaging elements, until the cap is turned to a defined position where those elements may disengage and permit the plunger to be drawn upwardly.
A typical bottle for containing a liquid to be dispensed by the apparatus of this invention will have a neck with external screw threads. The one end (the lower end, in use) of the casing may be provided with internal threads engageable with those of the neck to secure the casing to the bottle but in alternative embodiments, the one end of the casing is provided with resilient, inwardly directed fingers which are engageable behind formations on the neck of the bottle, to secure the casing in position. Suitable profiling of the neck of the bottle and of the fingers may make it impossible to remove the casing without destroying one or the other of the casing or the bottle neck, so as to eliminate the likelihood of contamination of the liquid in the bottle, once opened.